1. Field of the Invention
The present invention relates to a light emitting device and a manufacturing method thereof.
2. Description of the Background Art
Light emitting devices such as light emitting diodes and semiconductor laser devices which are formed of III-V group nitride system semiconductors such as GaN, AlGaN, InGaN and InAlGaN are receiving a great deal of attention because they are capable of, by direct transition, light emission in the yellow to ultraviolet region, especially in the blue region, with large luminous intensity.
FIG. 8 is a schematic cross-sectional view showing a conventional light emitting diode composed of III-V group nitride system semiconductors.
In FIG. 8, formed in order on a sapphire substrate 101 are a GaN buffer layer 102, an n-type GaN contact layer 103 also serving as an n-type cladding layer, an InGaN active layer 104, a p-type AlGaN cladding layer 105, and a p-type GaN contact layer 106. A p electrode 107 is formed on the p-type GaN contact layer 106 and an n electrode 108 is formed on the n-type GaN contact layer 103.
The individual layers of this light emitting diode are grown by metal organic chemical vapor deposition (MOCVD) at the growth temperatures shown in Table 1, for example.
TABLE 1 ______________________________________ Name of layer Growth temperature (.degree.C.) ______________________________________ Buffer layer 102 600 N-type contact layer 103 1150 Active layer 104 860 P-type cladding layer 1150 105 P-type contact layer 106 1150 ______________________________________
When manufacturing this light emitting diode, the p-type AlGaN cladding layer 105 is formed on the InGaN active layer 104 at a growth temperature higher than that for the InGaN active layer 104 to achieve good crystallinity. The growth of the p-type AlGaN cladding layer 105 at such a high temperature causes elimination of constituent elements such as In from the InGaN active layer 104. The crystallinity of the InGaN active layer 104 is thus deteriorated when crystal-growing the p-type AlGaN cladding layer 105. This causes difficulty in achieving larger luminous intensity with the light emitting diode.